In this research, for the first time, we present the evaluation of a semi-continuous pit manure recharge system on the mitigation of ammonia (NH₃) and hydrogen sulfide (H₂S) emissions from a swine finisher barn. The pit recharge system is practiced on many swine farms in the Republic of Korea, primarily for improving air quality in the barn. It consists of an integrated waste management system where the fraction of stored manure is pumped out (10× of the daily production of manure, 3× a day); solids are separated and composted, while the aerobically treated liquid fraction is then returned to the pit. We compared emissions from two 240-pig rooms, one equipped with a pit recharge system, and the other operating a conventional slurry pit under the slatted floor. Mean reduction of NH₃ and H₂S emissions were 49 ± 6% and 82 ± 7%, respectively, over 14 days of measurements. The removal efficiency of H₂S was higher than NH₃, likely because the pH of aerobically treated liquid manure remained slightly above 8. More work is warranted to assess the N balance in this system and the emissions of odor and greenhouse gasses (GHGs). It is also expected that it will be possible to control the NH₃ and H₂S removal rates by controlling the nitrification level of the liquid manure in the aerobic treatment system.

Environmental impact associated with odor and gaseous emissions from animal manure is one of the challenges for communities, farmers, and regulatory agencies. Microbe-based manure additives treatments are marketed and used by farmers for mitigation of emissions. However, their performance is difficult to assess objectively. Thus, comprehensive, practical, and low-cost treatments are still in demand. We have been advancing such treatments based on physicochemical principles. The objective of this research was to test the effect of the surficial application of a thin layer (¼ inches; 6.3 mm) of biochar on the mitigation of gaseous emissions (as the percent reduction, % R) from swine manure. Two types of biochar were tested: highly alkaline and porous (HAP) biochar made from corn stover and red oak (RO), both with different pH and morphology. Three 30-day trials were conducted with a layer of HAP and RO (2.0 & 1.65 kg∙m⁻², respectively) applied on manure surface, and emissions of ammonia (NH₃), hydrogen sulfide (H₂S), greenhouse gases (GHG), and odorous volatile organic compounds (VOCs) were measured. The manure and biochar type and properties had an impact on the mitigation effect and its duration. RO significantly reduced NH₃ (19–39%) and p-cresol (66–78%). H₂S was mitigated (16~23%), but not significantly for all trials. The phenolic VOCs had relatively high % R in most trials but not significantly for all trials. HAP reduced NH₃ (4~21%) and H₂S (2~22%), but not significantly for all trials. Significant % R for p-cresol (91~97%) and skatole (74~95%) were observed for all trials. The % R for phenol and indole ranged from (60~99%) and (29~94%) but was not significant for all trials. The impact on GHGs, isobutyric acid, and the odor was mixed with some mitigation and generation effects. However, larger-scale experiments are needed to understand how biochar properties and the dose and frequency of application can be optimized to mitigate odor and gaseous emissions from swine manure. The lessons learned can also be applicable to surficial biochar treatment of gaseous emissions from other waste and area sources.

Gaseous emissions, a side effect of livestock and poultry production, need to be mitigated to improve sustainability. Emissions of ammonia (NH₃), hydrogen sulfide (H₂S), greenhouse gases (GHGs), and odorous volatile organic compounds (VOCs) have a detrimental effect on the environment, climate, and quality of life in rural communities. We are building on previous research to bring advanced oxidation technologies from the lab to the farm. To date, we have shown that ultraviolet A (UV-A) has the potential to mitigate selected odorous gases and GHGs in the context of swine production. Much less research on emissions mitigation has been conducted in the context of poultry production. Thus, the study objective was to investigate whether the UV-A can mitigate NH₃, H₂S, GHGs, and O₃ in the simulated poultry barn environment. The effects of several variables were tested: the presence of photocatalyst, relative humidity, treatment time, and dust accumulation under two different light intensities (facilitated with fluorescent and light-emitting diode, LED, lamps). The results provide evidence that photocatalysis with TiO₂ coating and UV-A light can reduce gas concentrations of NH₃, CO₂, N₂O, and O₃, without a significant effect on H₂S and CH₄. The particular % reduction depends on the presence of photocatalysts, relative humidity (RH), light type (intensity), treatment time, and dust accumulation on the photocatalyst surface. In the case of NH₃, the reduction varied from 2.6–18.7% and was affected by RH and light intensity. The % reduction of NH₃ was the highest at 12% RH and increased with treatment time and light intensity. The % reduction of NH₃ decreased with the accumulation of poultry dust. The % reduction for H₂S had no statistical difference under any experimental conditions. The proposed treatment of NH₃ and H₂S was evaluated for a potential impact on important ambient air quality parameters, the possibility of simultaneously mitigating or generating GHGs. There was no statistically significant change in CH₄ concentrations under any experimental conditions. CO₂ was reduced at 3.8%–4.4%. N₂O and O₃ concentrations were reduced by both direct photolysis and photocatalysis, with the latter having greater % reductions. As much as 6.9–12.2% of the statistically-significant mitigation of N₂O was observed. The % reduction for O₃ ranged from 12.4–48.4%. The results warrant scaling up to a pilot-scale where the technology could be evaluated with economic analyses.

Inoculation is a widely used method to improve the efficiency of anaerobic digestion (AD) with a high organic load. This study was conducted to prove the potential of dairy manure as an inoculum source for AD of swine manure. Furthermore, an appropriate inoculum-to-substrate (I/S) ratio was determined to improve methane yield and reduce the required time of AD. We carried out 176 days of anaerobic digestion for five different I/S ratios (3, 1, and 0.3 on a volatile solid basis, dairy manure alone, and swine manure alone) of manure, using solid container submerged lab-scale reactors in mesophilic conditions. As a result, solid-state swine manure inoculated with dairy manure could be digested without inhibition caused by ammonia and volatile fatty acid accumulation. The highest methane yield potential was observed in I/S ratios 1 and 0.3, as 133 and 145 mL CH₄·g⁻¹-VS, respectively. The lag phase of swine manure alone was more extended, 41 to 47 days, than other treatments containing dairy manure, directly related to tardy startup. These results revealed that dairy manure can be used as an inoculum source for AD of swine manure. The proper I/S ratios leading to successful AD of swine manure were 1 and 0.3.

Odor and gaseous emissions from the swine industry are of concern for the wellbeing of humans and livestock. Additives applied to the swine manure surface are popular, marketed products to solve this problem and relatively inexpensive and easy for farmers to use. There is no scientific data evaluating the effectiveness of many of these products. We evaluated 12 manure additive products that are currently being marketed on their effectiveness in mitigating odor and gaseous emissions from swine manure. We used a pilot-scale system simulating the storage of swine manure with a controlled ventilation of headspace and periodic addition of manure. This dataset contains measured concentrations and estimated emissions of target gases in manure headspace above treated and untreated swine manure. These include ammonia (NH₃), hydrogen sulfide (H₂S), greenhouse gases (CO₂, CH₄, and N₂O), volatile organic compounds (VOC), and odor. The experiment to test each manure additive product lasted for two months; the measurements of NH₃ and H₂S were completed twice a week; others were conducted weekly. The manure for each test was collected from three different farms in central Iowa to provide the necessary variety in stored swine manure properties. This dataset is useful for further analyses of gaseous emissions from swine manure under simulated storage conditions and for performance comparison of marketed products for the mitigation of gaseous emissions. Ultimately, swine farmers, the regulatory community, and the public need to have scientific data informing decisions about the usefulness of manure additives.

Gaseous emissions from animal production systems affect the local and regional air quality. Proven farm-scale mitigation technologies are needed to lower these emissions and to provide management practices that are feasible and sustainable. In this research, we evaluate the performance of a unique approach that simultaneously mitigates emissions and improves air quality inside a barn equipped with a manure pit recharge system. Specifically, we tested the effects of summertime feeding rations (used by farmers to cope with animal heat stress) and manure management. To date, the pit recharge system has been proven to be effective in mitigating both ammonia (NH₃; approximately 53%) and hydrogen sulfide (H₂S; approximately 84%) emissions during mild climate conditions. However, its performance during the hot season with a high crude protein diet and high nitrogen loading into the pit manure recharge system is unknown. Therefore, we compared the emissions and indoor air quality of the rooms (240 pigs, ~80 kg each) equipped with a conventional slurry and pit recharge system. The main findings highlight the importance and impact of seasonal variation and diet and manure management practices. We observed 31% greater NH₃ emissions from the pit recharge system (33.7 ± 1.4 g·head⁻¹·day⁻¹) compared with a conventional slurry system (25.9 ± 2.4 g·head⁻¹·day⁻¹). Additionally, the NH₃ concentration inside the barn was higher (by 24%) in the pit recharge system compared with the control. On the other hand, H₂S emissions were 55% lower in the pit recharge system (628 ± 47 mg·head⁻¹·day⁻¹) compared with a conventional slurry pit (1400 ± 132 mg·head⁻¹·day⁻¹). Additionally, the H₂S concentration inside the barn was lower (by 54%) in the pit recharge system compared with the control. The characteristics of the pit recharge liquid (i.e., aerobically treated manure), such as the total nitrogen (TN) and ammonium N (NH₄-N) contents, contributed to the higher NH₃ emissions from the pit recharge system in summer. However, their influence on H₂S emissions had a relatively low impact, i.e., emissions were still reduced, similarly as they were in mild climate conditions. Overall, it is necessary to consider a seasonal diet and manure management practices when evaluating emissions and indoor air quality. Further research on minimizing the seasonal nitrogen loading and optimizing pit recharge manure characteristics is warranted.